Multi-phasic microphotodiode retinal implant and adaptive imaging retinal stimulation system

ABSTRACT

An artificial retina device and a method for stimulating and modulating its function is disclosed. The artificial retina device is comprised of plural multi-phasic microphotodiode subunits. In persons suffering from blindness due to outer retinal layer damage, a plurality of such devices, when surgically implanted into the subretinal space, may allow useful formed artificial vision to develop. One device, called a MMRI- 4,  transduces light into electric currents to stimulate the retina. The four microphotodiode subunits of the MMRI- 4  are oriented so that each flattened sides of the MMRI- 4  has two subunits in a PiN configuration and two subunits in a NiP configuration. The flattened cubic shape of the MMRI- 4  will allow one or the other of the two flattened sides to be preferentially directed toward incident light when implanted in the subretinal space. Because both the PiN and NiP configurations are present on each of the flattened sides of the MMRI- 4,  electric currents which produce the sensation of light from a PiN current, or darkness from a NiP current, can be induced regardless of which the flattened photoactive sides faces incident light. Filter layers disposed on the PiN configuration will allow visible light to induce a PiN current, and filter layers disposed on the NiP configuration will allow infrared light to induce a NiP current. By projecting real or computer controlled visible light images, and computer controlled infrared light images or illumination, simultaneously or in rapid alternation onto the MMRI- 4 s, the nature of induced retinal images may be modulated and improved. An Adaptive Imaging Retinal Stimulation System (AIRES), with a Projection and Tracking Optical System (PTOS), which may be worn as a headset is used for this purpose, and is also disclosed. Color images may even be induced by programming the stimulating pulse durations and frequencies of the AIRES system. By creating both PiN and NiP currents, in close spatial positions and temporal sequences, electrolysis damage to cellular tissue from prolonged unidirectional electric currents is reduced. MMRI- 4 s may also be embedded in a flexible, biologically compatible sheet, with its electrodes exposed on both surfaces of the sheet. This sheet is then implanted on the nerve fiber layer surface of the retina, where electrical stimulation can also induce a form of artificial vision.

[0001] This is a Continuation-In-Part of U.S. patent application Ser.No. 08/465,766, filed Jun. 6, 1995.

BACKGROUND OF THE INVENTION

[0002] The present invention is a medical product that can be used tocorrect vision loss or even complete blindness caused by certain retinaldiseases. A variety of retinal diseases cause vision loss or blindnessby destruction of the vascular layers of the eye including the choroid,choriocapillaris, and the outer retinal layers including Bruch'smembrane and retinal pigment epithelium. Loss of these layers isfollowed by degeneration of the outer portion of the inner retinabeginning with the photoreceptor layer. Variable sparing of theremaining inner retina composed of the outer nuclear, outer plexiform,inner nuclear, inner plexiform, ganglion cell and nerve fiber layers,may occur. The sparing of the inner retina allows electrical stimulationof this structure to produce sensations of light.

[0003] Prior efforts to produce vision by electrically stimulatingvarious portions of the retina have been reported. One such attemptinvolved an externally powered photosensitive device with itsphotoactive surface and electrode surfaces on opposite sides. The devicetheoretically would stimulate the nerve fiber layer via direct placementupon this layer from the vitreous body side. The success of this deviceis unlikely due to it having to duplicate the complex frequencymodulated neural signals of the nerve fiber layer. Furthermore, thenerve fiber layer runs in a general radial course with many layers ofoverlapping fibers from different portions of the retina. Selection ofappropriate nerve fibers to stimulate to produce formed vision would beextremely difficult, if not impossible.

[0004] Another device involved a unit consisting of a supporting baseonto which a photosensitive material such as selenium was coated. Thisdevice was designed to be inserted through an external scleral incisionmade at the posterior pole and would rest between the sclera andchoroid, or between the choroid and retina. Light would cause apotential to develop on the photosensitive surface producing ions thatwould then theoretically migrate into the retina causing stimulation.However, because that device had no discrete surface structure torestrict the directional flow of charges, lateral migration anddiffusion of charges would occur thereby preventing any acceptableresolution capability. Placement of that device between the sclera andchoroid would also result in blockage of discrete ion migration to thephotoreceptor and inner retinal layers. That was due to the presence ofthe choroid, choriocapillaris, Bruch's membrane and the retinal pigmentepithelial layer all of which would block passage of those ions.Placement of the device between the choroid and the retina would stillinterpose Bruch's membrane and the retinal pigment epithelial layer inthe pathway of discrete ion migration. As that device would be insertedinto or through the highly vascular choroid of the posterior pole,subchoroidal, intraretinal and intraorbital hemorrhage would likelyresult along with disruption of blood flow to the posterior pole. Onesuch device was reportedly constructed and implanted into a patient'seye resulting in light perception but not formed imagery.

[0005] A photovoltaic device artificial retina was also disclosed inU.S. Pat. No. 5,024,223. That device was inserted into the potentialspace within the retina itself. That space, called the subretinal space,is located between the outer and inner layers of the retina. The devicewas comprised of a plurality of so-called Surface ElectrodeMicrophotodiodes (“SEMCPs”) deposited on a single silicon crystalsubstrate. SEMCPs transduced light into small electric currents thatstimulated overlying and surrounding inner retinal cells. Due to thesolid substrate nature of the SEMCPs, blockage of nutrients from thechoroid to the inner retina occurred. Even with fenestrations of variousgeometries, permeation of oxygen and biological substances was notoptimal.

[0006] Another method for a photovoltaic artificial retina device wasreported in U.S. Pat. No. 5,397,350, which is incorporated herein byreference. That device was comprised of a plurality of so-calledIndependent Surface Electrode Microphotodiodes (ISEMCPs), disposedwithin a liquid vehicle, also for placement into the subretinal space ofthe eye. Because of the open spaces between adjacent ISEMCPs, nutrientsand oxygen flowed from the outer retina into the inner retinal layersnourishing those layers. In another embodiment of that device, eachISEMCP included an electrical capacitor layer and was called anISEMCP-C. ISEMCP-Cs produced a limited opposite direction electricalcurrent in darkness compared to in the light, to induce visualsensations more effectively, and to prevent electrolysis damage to theretina due to prolonged monophasic electrical current stimulation.

[0007] These previous devices (SEMCPs, ISEMCPs, and ISEMCP-Cs) dependedupon light in the visual environment to power them. The ability of thesedevices to function in continuous low light environments was, therefore,limited. Alignment of ISEMCPs and ISEMCP-Cs in the subretinal space sothat they would all face incident light was also difficult.

SUMMARY OF THE INVENTION

[0008] This invention is, among other things, a system that allows forimplantation of microscopic implants into the diseased eye so that thesystem can function in continuous low light levels, and also produceimproved perception of light and dark details. This invention has twobasic components: (1) multi-phasic microphotodiode retinal implants(“MMRIs”) of microscopic sizes that are implanted into the eye, and (2)an externally worn adaptive imaging retinal stimulation system (“AIRES”)that, among other things, uses infrared light to stimulate the MMRIs toproduce “dark current” in the retina during low light conditions, and toimprove perception of light and dark details.

[0009] In its basic form, a MMRI of this invention has, depending uponits orientation, a PiN configuration where the P-side of the implant haslight filter layer that permits visible light to pass, and where theN-side of the implant has a light filter that permits only infrared(“IR”) light to pass, and preferably only selected wavelength(s) of IRlight. In practice, a population of such MMRIs are implanted in theso-called “subretinal space” between the outer and inner retina in theeye such that, randomly, about half of them (i.e. the firstsubpopulation) will be oriented so that their P sides face lightincident to the eye, and about the other half (i.e. the secondsubpopulation) will be oriented so that their N-sides face lightincident to the eye.

[0010] In this location and orientation, the first subpopulation ofMMRIs convert energy from incoming visible light into small electricalcurrents to stimulate the sensation of light in the eye to produceformed vision. In other words, the first subpopulation converts visiblelight to electrical current to stimulate the retina with “lightcurrents” to induce the perception of visible light. The secondsubpopulation of MMRIs converts infrared light provided by AIRES intoelectrical currents to stimulate the retina with “dark currents” duringlow light conditions to induce the perception of darkness.

[0011] The adaptive imaging retinal stimulation system or AIRES iscomprised of a projection and tracking optical system (“PTOS”), aneuro-net computer (“NNC”), an imaging CCD camera (“IMCCD”), and aninput stylus pad (“ISP”).

[0012] In one embodiment of this invention, each microscopic implantcomprises plural paired MMRI subunits disposed together in a singleflattened cubic unit. The microscopic implants are fabricated so thateach MMRI member of each pair has its positive pole electrode on one ofthe flattened surfaces, and its negative pole electrode on the otherflattened surface. Each MMRI member of each pair is disposed so that itis oriented in the opposite direction from the other MMRI member of thepair, the negative (N) electrode of the first MMRI pair member being onor close to the same surface as the positive (P) electrode of the secondMMRI pair member, and the positive electrode of the first MMRI pairmember being on or close to the same surface as the negative electrodeof the second MMRI pair member. Each of the flattened sides of a singlemicroscopic implant therefore, has at least one associated positivemicrophotodiode electrode from one MMRI and one negative microphotodiodeelectrode from another MMRI. This symmetry ensures that each suchmicroscopic implant functions in exactly the same manner regardless ofwhich of the flattened surfaces faces incident light. Multiple layerdielectric filters are disposed on the P surfaces and N surfaces of theMMRI subunits to allow visible light (400 to 740 nm) to pass through tothe P surfaces and infrared light (740-900 nm) to pass through to the Nsurfaces. In this manner, the PiN configuration of each MMRI subunitresponds to visible light while the NiP configuration responds toinfrared light.

[0013] In a modification of this embodiment, a common electrode, on eachside of the implant, connects the positive pole electrode of one MMRImember to the negative pole electrode of the second MMRI member on thesame side.

[0014] In the preferred embodiment, the flattened microscopic implantstructures typically have a thickness to width and depth ratio of 1:3and have a preference to orient themselves, within the subretinal space,with one of their flattened photoactive surfaces positioned to acceptincident light. The P and N electrodes of each MMRI subunit, and/or thecommon electrode connecting the P and N electrodes, are on or close tothe microscopic implant's light sensitive surfaces. Electric currentsproduced by the PiN configuration will stimulate the sensation of“light” in the overlying and/or adjacent retinal cells, while electriccurrents produced by the NiP configuration will stimulate the sensationof “darkness” in the vicinity of those same cells.

[0015] The power for the “light currents” is derived from the visiblespectrum of light from incoming images. The power for the “darkcurrents” is provided by superimposed infrared (JR) light and/or imagesprojected into the eye by an external computer-controlled opticalheadset system. This external computer controlled headset projectionsystem is the second component of the artificial retinal device of thisinvention and is called the Adaptive Imaging Retinal Stimulation System“AIRES”.

[0016] AIRES is comprised of component sub-systems of: a Projection andTracking Optical System (PTOS), a Neuro-Net Computer (NNC), an ImagingCCD Camera (IMCCD), and an Input Stylus Pad (ISP). During operation,AIRES “sees” and interprets details and characteristics of images viaits own IMCCD and processes this information with its NNC. It thenprojects modulated infrared light and/or images, and visible lightimages if necessary into the eye to modify implant function. By the useof a partially reflective and transmissive mirror in the PTOS, AIRESprojects IR and visible light/images that are superimposed over thevisible spectrum images passing into the eye from the environment.Initially, AIRES will be programmed using “patient input” from an inputdevice, such as a stylus pad, to “train” the NNC on how to modifyimplant function to produce accurate images. After training, AIRES willhave an improved capability to modulate implant function with littleadditional patient assistance. The primary advantages of this MMRI plusAIRES combination system over the previous art is that the combinedsystem can still function in low light environments and that “light” and“dark” currents may be finely tuned by AIRES to provide optimal images.The production of opposing light and dark currents will also decreaseany damaging effects from electrolysis, and improve implantbiocompatibility.

[0017] In the preferred embodiment, the AIRES PTOS headset is worn bythe patient, and projects variable intensity IR and visible-light imagesand illumination into the eye, by using an IR and visible-light capableCRT (IRVCRT). These IR and visible-light images and illumination willmodify the function of the MMRI subunits of the implant by modulatingtheir current output. In darkness, IR illumination is the predominatepower source and powers the MMRI NiP configuration to produce electriccurrents that will stimulating the visual sensation of darkness.However, the IR induced NiP current is modified by the PTOS through NNCcontrol, based upon information provide by the PTOS's ambient lightsensors and IMCCD. Under bright lighting conditions, a higher currentwill be induced in the MMRI PiN configuration by ambient light, and willoffset a modulated lower MMRI NiP current. This produces a netperception of light. Because images in the normal environment haveconstantly changing light and dark qualities, the implants will alsorapidly change their electrical outputs between “light currents” and“dark currents”. Modulation of the implant “light current” can also beperformed by the AIRES PTOS by projecting additional visible lightimages, superimposed over the ambient light images.

[0018] During operation, AIRES uses its NNC to process digitized imagesprovided by its IMCCD. In the preferred embodiment, AIRES projectssuperimposed, real-time-video, visible and infrared images onto theretinal implants. These images may be displayed either simultaneously orin rapid succession from the IRVCRT. Alternatively, any appropriatedisplay device such as a filtered active matrix LCD, LED display, orfiltered plasma display may be used to produce the visible and IR lightand images. AIRES controls the PTOS projected images by changing theirwavelengths, intensity, duration, and pulse frequency. A patient inputdevice (e.g. an Input Stylus Pad) is also interfaced with the NNC andallows the patient to modify the IR and visible light images produced bythe PTOS headset. This patient “feedback” is analyzed by the AIRES NNC,then compared with the computer processed images from the IMCCD, and thedifferences learned by the AIRES Neuro-Net software. After a teachingperiod, the NNC is able to automatically adjust the computer generatedvisible and IR images to improve image quality without assistance by thepatient. By adjusting the stimulating frequency and duration of the PTOSIR and visible images, AIRES will also be able to stimulate thesensation of color in some patients. This is in a manner similar tocolor sensations induced in normal sighted persons, by using a spinningblack and white Benham top, or by using frequency modulated black andwhite television monitors.

[0019] The MMRI and AIRES components of this invention differ from theprevious art primarily in the following ways. Visible and infraredimages and light are used to selectively modulate MMRI function. A MMRIcan be stimulated with light from either of its two photoactive sidesand produce localized stimulating electric current from both sides. Theflattened shapes of the MMRIs allow preferential orientation of thedevices toward incident light when disposed in the subretinal space.Using the AIRES system, electrical output from MMRIs can be programmedfor individual patient needs. The design of the MMRIs also allows thealternative to use them to stimulate the nerve fiber layer, ganglioncell layer, or inner plexiform layer of retina from vitreous body side;or to use them to stimulate the remnant photoreceptor layer, bipolarcell layer, or the inner plexiform layer from the subretinal space, byreversing their polarities during fabrication. The biphasic nature ofthe electrical current output from MMRIs are also better toleratedbiologically than the mostly monophasic nature of electrical stimulationof the previous art.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is a plan view of one embodiment of the microphotodioderetinal implant of this invention (MMRI);

[0021]FIG. 2 is a cross-section taken along the plane of the line II-IIof FIG. 1;

[0022]FIG. 3 is a plan view of a second embodiment of this invention(MMRI-E);

[0023]FIG. 4 is a cross-section taken along the plane of the line IV-IVof FIG. 3;

[0024]FIG. 5 shows the manufacturing process of the microphotodioderetinal implant of FIG. 1 (MMRI);

[0025]FIG. 6 is a plan view of a third embodiment of this invention(MMRI-4), which is composed of two pairs of MMRI subunits;

[0026]FIG. 7 is a perspective view in cross-section taken along theplane of line VI-VI of FIG. 6;

[0027]FIG. 8 is a plan view of a fourth embodiment of this invention(MMRI-4E), which is composed of two pairs of MI-E subunits;

[0028]FIG. 9 is a perspective view in cross-section taken along theplane of line VIII-VIII of FIG. 8;

[0029]FIG. 10 shows three dimensional and plan views, and a magnifiedinset view of a 3 inch silicon wafer secured onto a thicker 4 inchsilicon wafer during the manufacture of the microphotodiode retinalimplants (MMRI-4) of FIG. 6;

[0030]FIG. 11 shows the microphotodiode retinal implants (MMRI-4) ofFIG. 6 implanted in the preferred location of the subretinal space;

[0031]FIG. 12 shows the microphotodiode retinal implants (MMRI-4) ofFIG. 6 implanted in an alternate location, on the nerve fiber layersurface of the retina;

[0032]FIG. 13 shows a plan view of a fifth embodiment of themicrophotodiode implant of this invention (MMRI-IPV);

[0033]FIG. 14 is a cross-section take along the plane of line X-X ofFIG. 13.

[0034]FIG. 15 shows a plan view of a sixth embodiment of themicrophotodiode implant of this invention (MMRI-IPIR);

[0035]FIG. 16 is a cross-section taken along the plane of line XII-XIIof FIG. 15;

[0036]FIG. 17 shows a plan view of a seventh embodiment of themicrophotodiode implant of this invention (MI-IPVIR-A);

[0037]FIG. 18 is a cross-section taken along the plane of line XIV-XIVof FIG. 17;

[0038]FIG. 19 shows a plan view of a eighth embodiment of themicrophotodiode implant of this invention (MMRI-IPVIR-B);

[0039]FIG. 20 is a cross-section taken along the plane of line XVI-XVIof FIG. 19;

[0040]FIG. 21 is a cross-section of the retina showing themicrophotodiode implants of FIG. 17 (MMRI-IPVIR-A) in their preferredlocation in the subretinal space, with their electrodes penetrating intothe sublamina B, and sublamina A locations of the inner plexiform;

[0041]FIG. 22 is a cross-section of the retina showing themicrophotodiode implants of FIG. 17 with reversed polarities(MMRI-IPVIR-AR), in a ninth embodiment of this invention, in theirpreferred location on the nerve fiber layer surface, with theirelectrodes penetrating into the sublamina B, and sublamina A location ofthe inner plexiform;

[0042]FIG. 23 is a generalized schematic diagram of the Adaptive ImagingRetinal Stimulation System (AIRES) showing its component sub-systems of:the Projection and Tracking Optical System (PTOS), the Neuro-NetComputer (NNC), and the Input Stylus Pad (ISP). Q-SEMCPs are shownimplanted in the eye;

[0043]FIG. 24 A-D shows a PTOS device configured as a glasses headset,and the schematic of its optics;

[0044]FIG. 25 shows the components of the AIRES system, consisting ofthe PTOS, the NNC, and ISP.

[0045]FIG. 26 is a plan view (containing a detail exploded inset view)of a large wafer containing-a ninth embodiment of an implant of thisinvention (“MMRI-OPSISTER-D”).

[0046] FIGS. 27 A-E are perspective views in cross-section taken alongthe plane of line XXVI-XXVI of FIG. 26 showing the fabrication steps anthe MMRI-OPSISTER-D of FIG. 26.

[0047]FIG. 28 shows MMRI-OPSISTER-D devices used in a small chip with abeveled edge and implanted into the subretinal space.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0048] In a preferred embodiment of this invention (FIG. 1-2), eachmicrophotodiode implant (106) is fabricated as a flattened cubic device(hereafter MMRI) containing a single two-side microphotodiode. In thispreferred embodiment, each MMRI (106) forms the shape of a flattenedcube with rounded corners and edges, and is sized in microscopicdimensions, and is a physically independent unit. MMRIs (106) mayfunction as a PiN or NiP device, depending upon which of its twophotosensitive sides, the P-side (107 a) or the N-side (107 b) isstimulated by visible and/or infrared light (108). From top to bottom,the layers of the MMRI (106) include the P electrode (110) preferablymade of P doped polysilicon, a multilayer dielectric filter (122) toallow passage of only visible light (400 nm to 740 nm) to the next P+layer (112), a contact pad (114) fabricated from any or all or compoundsof the following: gold, aluminum, titanium, and chromium, to establishelectrical contact between layers (110) and (112), an intrinsic layer(126) which forms naturally between the P+ layer (112) and the N-typesilicon substrate (128), a N+ layer (118), a multilayer dielectricfilter (124) to allow passage of only infrared light (740 nm to 900 nm)to the N+ layer (118), a contact pad (120) fabricated from any or allcompounds of the following: gold, aluminum, titanium, and chromium toestablish electrical contact between the N+ layer (118) and the lastlayer that is the N electrode (116), preferably made of N-dopedpolysilicon.

[0049] Although FIG. 1-2 shows that the P electrode (110) and the Nelectrode (116) cover the entire surface of the MMRI (106), in alternateembodiments, the P electrode (110) may cover a fraction of thephotosensitive side P-side (107a), and the N electrode (116) may cover afraction of the photosensitive side N-side (107 b). These fractions mayrange from 0.1% to 99.9%. The purpose of fractional coverage of the Pelectrode (110) and N electrode (116) is to allow concentration ofelectric currents produced by the MMRI (106). Also as shown in FIGS.1-2, the width and depth of the MMRI (106) are the same dimensions andmay vary between 5 μm and 100 μm, and the height is 25% to 50% that ofthe width and depth. However, in alternate embodiments, MMRIs (106) maybe manufactured as small as 1 μm and as large as 2000 μm in depth andwidth, and the width and depth need not be the same; and the height ofthe MMRI may be from 1% to 500% of the width and depth. Preferably, theMMRI N-type silicon substrate (128) has an ohmic resistive value between50 and 2000 ohm-cm2. However, in alternate embodiments, the MMRI N-typesubstrate (128) may have ohmic resistive values of between 1 ohm-cm2 and100,000 ohm-cm2. The designed and preferred electric current output ofeach MMRI (106) is on the order of 1 to 5000 nA depending on incidentlighting (108). Nevertheless, a range of 0.01 nA to 200,000 nA is alsosuitable.

[0050] In a second embodiment of this invention (MMRI-E) (FIG. 3-4), theMMRIs of FIGS. 1-2 are fabricated so that the polysilicon layer 110 issandwiched between the multi-layer dielectric visible light filter layer122 and the P+ layer 112, and the polysilicon layer 116 is sandwichedbetween the multi-layer dielectric IR filter layer 124 and the N+ layer124. The aluminum contact pads 114 and 120 of FIGS. 1-2 are not beneeded in this embodiment. This embodiment results in MMRI-Es whichpredominately stimulated retinal cells adjacent to the MMRI-Es ratherthan on top of the MMRI-Es. This second embodiment is used in thosepatients where side simulation will induce better vision than topstimulation. The remaining layers of the intrinsic layer 126, and theN-type silicon substrate layer 128, the P-side 107 a, and the N-side 107b are unchanged.

[0051]FIG. 5, A through L illustrates the manufacturing steps of thepreferred MMRIs. As shown in FIG. 5A, a 3″ float zone 1-0-0 N-typesilicon wafer (140) at 200 to 400 ohm-cm is thinned to 8 μm, and asilicon support ring (142) 0.4″ to 0.5″ wide (prepared by chemical etchand channel stop techniques to have 30-40 degree i.d. taper) is thenoxide bonded to target wafer (140). As shown in FIG. 5B, P+ layer (144)is ion implanted to 0.2 μm depth on one side of the wafer (140). Theother side is masked from the implantation. As shown in FIG. 5C, wafer(140) is flipped over and the N+ layer (146) is ion implanted to 0.2 μmdepth on the second side. The first P+ side (144) is masked fromimplantation.

[0052] As shown in FIG. 5D, both the P+ (144) and N+ (146) layers arethermally driven to 0.5 μm to 0.6 μm depth. As shown in 5E, Multiplealternating layers of TiO₂ and quartz are evaporation deposited toproduce an interference filter (148) to pass 400-740 nm visible light,but stops 740-900 nm IR light on the P+ side (144). The total thicknessof this dielectric layer (148) is about 3.5 to 5 μm. As shown in FIG.5F, the wafer is flipped over to expose the N+ side (146) and multiplealternating layers of TiO₂ are evaporation deposited to produce ainterference filter (150) which passes 740 900 nm IR light, but stops400-740 nm visible light on the N+ side (146). Total thickness of thisdielectric layer (150) is about 2-3 μm. In FIG. 5G, photoresist isspun-on and both sides of the wafer (140) are patterned with 8 μm×8 μmcontact holes (152) which penetrate the interference films (148 and 150)to the P+ layer (144) and the N+ layer (146), with hole spacing of 50 μmin a square grid fashion. As shown in FIG. 5H, 1.0 μm of aluminum (152)is deposited to both sides of the wafer (140). In FIG. 5I, photoresistis spun-on and both sides of the wafer (140) are patterned to leave 12μm×12 μm aluminum contact pads (154) over all the 8 μm×8 μm contactholes, and then thermally drive in the aluminum. In FIG. 5J, plasmaassisted, low pressure, chemical vapor deposition is used to deposit 0.2μm to 0.5 μm of P+ polysilicon (156) on the P+ side interference filter(148) of the wafer (140) to establish electrical contact with thealuminum contact pads (154), at 250° 300° C. The other side of wafer ismasked. In FIG. 5K, plasma assist, low pressure, chemical vapor is usedto deposit 0.2 μm to 0.5 μm of N+ polysilicon (158) on N+ sideinterference filter (150) of the wafer (140) to establish electricalcontact with the aluminum contact pads (154), at 250+ 300° C. The otherside of wafer is masked. In FIG. 5L, the 3 inch wafer is eximer lasercut into 50 μm×50 μm squares (160) with one contact pad centered on eachside of every square. The final cleaned, washed, and recovered squaresare MMRIs. The MMRIs may be briefly tumbled in a glass container usingultrasonic energy to slightly round off the sharp corners and edges ofthe devices.

[0053] FIGS. 6-7 illustrate the layered microarchitecture of a thirdembodiment of the artificial retina device of this invention, designatedat (8), and is referred to for convenience as a MMRI-4 to distinguish itfrom other embodiments of this invention. MMRI-4 (8) forms the shape ofa flattened cube with rounded comers and edges, and is sized inmicroscopic dimensions. It is comprised of four microphotodiode subunits(10 a×2 and 10 b×2). Each microphotodiode subunit (10 a or 10 b) of theMMRI-4 (8) may be a PiN or NiP device, depending upon which of itsphotosensitive surfaces is oriented toward light (12). For example, asshown in FIG. 7, the near left microphotodiode (10 a) is behaving as aPiN subunit, because the P+ tub (14) is facing incident light (12). Incontrast, the near right microphotodiode (10 b) is behaving as a NiPsubunit because its N+ tub (18) is facing incident light (12). It can bereadily appreciated, that if the MMRI-4 (8) is flipped over, themicrophotodiode subunit (10 a) will have its N+ tub (18) facing incidentlight and will therefore behave as a NiP device. Similarly, when flippedover, the microphotodiode subunit (10 b) will have a P tub (14) facingincident light and will behave as a PiN device.

[0054] Further illustrated in FIGS. 6-7, the MMRI-4 (8) in its basicform contains four positive (P) electrodes (13) disposed on the four P+tub (14) surfaces on the top and bottom sides of the MMR-4 (8) (note thebottom structure of the two rear microphotodiode subunits cannot be seenin FIG. 7) The P electrodes (13) are preferably made of P dopedpolysilicon, produced by chemical vapor deposition, and are deposited onthe inner corners of the P+ tubs (14). Interposed between the Pelectrodes (13) and the P+ tubs (14), is a layer of gold, titanium orchromium (14 a) to promote adhesion and to act as a light block. TheMMRI-4 (8) also contains four negative (N) electrodes (16) disposed onthe four N+ tub (18) surfaces. The N electrodes (16) are preferably madeof N-doped polysilicon, produced by chemical vapor deposition, and aredeposited on the inner corners of the N+ tubs (18). Interposed betweenthe N electrodes (16) and the N+ tubs (18) is also a layer of gold,titanium or chromium (14 a) to promote adhesion and to act as a lightblock.

[0055] Alternatively, the P electrodes (13), and N electrodes (16) maybe constructed of any suitable material that will conduct electriccurrent. These conductive materials may include, but are not limited to,gold, chromium, aluminum, iridium, and platinum or any combination orcompounds made from these materials. The P electrodes (13) and the Nelectrodes (16) may cover any fraction, from 0.1% to 99.9%, of theirrespective P+ tub (14) or N+ tub (18) surfaces. Filter layers (20) aredisposed on the portion of the P+ tub (14) surfaces not covered by the Pelectrodes (13). These filter layers (20) are preferably fabricated frommulti-layer dielectric coatings and allow passage of only visible light(400 nm to 740 nm) to the P+ tub (14) surfaces. Filter layers (22) aredisposed on the N+ tub (18) surfaces not covered by the N electrodes(16). These filter layers (22), are also preferably fabricated frommulti-layer dielectric coatings and allow passage of only infrared light(740 to 900 μm) to the N+ tub (18) surfaces. Under each P+ tub (14), anintrinsic layer (15) forms naturally between the P+ tub (14) and theN-type silicon substrate (25). The N+ tub layers (18) are created by ionimplantation of additional N-type phosphorus into the N-type siliconsubstrate (25). Ion implantation of P-type boron around each MMRI-4subunit (10 a×2, 10 b×2) produces a channel stop (24) to electricallyseparate the microphotodiode subunits from each other. Outside thechannel stop material (24) is surrounding N-type silicon substrate (25b).

[0056] In the embodiment of the invention shown in FIGS. 6-7, the widthand depth of the MMRI-4 (8) are the same dimensions and are between 10and 50 microns, and the height is 25% to 50% that of the width anddepth. This flattened cubic configuration will allow one or the other ofthe two flattened photoactive sides of the MMRI-4 (8) to bepreferentially directed to incident light (12), when the MMRI-4 (8) isimplanted in the subretinal space. MMRI-4s (8) may be manufactured assmall as 1 micron and as large as 1000 microns in depth and width, andthe width and depth need not be the same; further the height of theMMRI-4 may be from 1% to 500% of negative (N) electrodes (16) disposedon the four N+ tub (18) surfaces. The transparent N electrodes (16) arepreferably made of N-doped polysilicon, produced by chemical vapordeposition, and are deposited on the N+ tubs (18).

[0057] Alternatively, the P electrodes (13), and N electrodes (16) maybe constructed of any suitable material that can be deposited in a thintransparent layer, and that will conduct electric current. Theseconductive materials may include, but are not limited to, gold,chromium, aluminum, iridium, and platinum or any combination orcompounds made from these materials. Filter layers (20) are disposed onthe P electrodes (13). These filter layers (20) are preferablyfabricated from multi-layer dielectric coatings and allow passage ofonly visible light (400 nm to 740 nm) through to the transparent Pelectrodes (13) and then to the P+ tub (14) surfaces. Filter layers (22)are disposed on the N+ tub (18) surfaces. These filter layers (22), arealso preferably fabricated from multi-layer dielectric coatings andallow passage of only infrared light (740 to 900 nm) through to thetransparent N electrodes (16) and then to the N+ tub (18) surfaces.Under each P+ tub (14), an intrinsic layer (15) forms naturally betweenthe P+ tub (14) and the N-type silicon substrate (25). The N+ tub layers(18) are created by ion implantation of additional N-type phosphorusinto the N-type silicon substrate (25). Ion implantation of P-type boronaround each MMRI-4 subunit (10 a×2, 10 b×2) produces a channel stop (24)to electrically separate the microphotodiode subunits from each other.Outside the channel stop material (24) is surrounding N-type siliconsubstrate (25 b).

[0058] In the embodiment of the invention shown in FIGS. 8-9, the widthand depth of the MMRI-4E (8 a) are the same dimensions and are between10 and 50 microns, and the height is 25% to 50% that of the width anddepth. This flattened cubic configuration will allow one or the other ofthe two flattened photoactive sides of the MMRI-4E (8 a) to bepreferentially directed to incident light (12), when the MMRI-4E (8 a)is implanted in the subretinal space. MMRI-4Es (8 a) may be manufacturedas small as 1 micron and as large as 1000 microns in depth and width,and the width and depth need not be the same; further the height of theMMRI-4E may be from 1% to 500% of the width and depth. In the embodimentof FIGS. 8-9, the MMRI-4E N type substrate (25 and 25 b) has an ohmicresistive value between 50 and 2000 ohm-cm². However, the MMRI-4E N-typesubstrate (25 and 25 b) may have ohmic resistive values of between 1ohm-cm² and 100,000 ohm-cm². The designed and preferred electric currentoutput of each MMRI-4E subunit microphotodiode (10 a or 10 b) is on theorder of 1 to 5000 nA depending on incident lighting (12). Nevertheless,a range of 0.01 nA to 200,000 nA may also be suitable. The MMRI-4E (8 a)may also be modified to achieve greater or lesser electrical output bychanging the thickness and therefore the transparency of each Pelectrode (13), and/or the N electrode (16).

[0059] In FIG. 10, and FIG. 10 inset, the manufacture of the preferredMMRI-4s (8) is illustrated. The first stage in the manufacture ofMMRI-4s begins with a three-inch diameter N type 1-0-0 silicon wafer(30) that is 8 microns thick. This wafer (30) is secured around itscircumference to a four-inch wafer (34) approximately 500 microns thick,with titanium pins (32). As shown in the FIG. 10 inset, a plurality ofN-type square island groups (8) that eventually become the MMRI-4s areisolated from the surrounding N-type substrate (25 b) by ionimplantation of P-type boron channel stops (24) from both sides. Thechannel stops (24) are heat driven through the entire thickness of thethree-inch diameter wafer (30) to isolate four square columns of N-typesilicon substrate (25) per square island (8). Each square column (25) is11 microns per side and separated from adjacent square columns (25) ofthe same MMRI-4 (8) by 1 micron of P-type silicon channel stop (24). Theresultant square islands (8), including the channel stops (24) are 21microns per side. The square islands (8) are separated from each otherby 1 micron of N-type silicon substrate (25 b). Alignment holes (36) areexcimer laser drilled through the three-inch wafer (30). These holes(36) facilitate alignment of fabrication masks from either side of thethree-inch wafer (30).

[0060] The P+ tubs (14) shown in FIG. 7 are created by ion implantationand thermal diffusion of P-type boron into the N-type substrate squarecolumns (25). Two P+ tubs (14) are formed on each side of the MMRI-4square island (8) and are arranged diagonally to each other. Intrinsiclayers (15) automatically form between the P+ tubs (14) and the N typesilicon substrate of the square columns (25). The N+ tubs (18) arecreated by ion implantation and thermal diffusion of additional N-typephosphorus into the N-type silicon substrate square columns (25) fromthe opposite side of the P+ tubs (14). After deposition of a gold,chromium or titanium layer (14 a) to improve adhesion and to act as alight block on the inner comers of all the P+ tubs (14) and N+ tubs(18), P-doped polysilicon electrodes (13) and the N-doped polysiliconelectrodes (16), each covering 10% of the P+ tub (14) and N+ tub (18)surfaces are then deposited on their respective P+ tubs (14) and N+ tubs(18). The three-inch wafer (30), still secured on the four-inch supportwafer (34), of FIG. 10 is then transferred to a vacuum depositionchamber where multilayer dielectric coatings (20), that bandwidth passvisible light (400-740 nm) are deposited on the P+ tubs (14) andmultilayer dielectric coatings (22) that bandwidth pass infrared lightare deposited on the N+ tubs (18). The three-inch wafer (30) is thenflipped over and re-secured on the four-inch support wafer (34). Again,multilayer dielectric coatings (20) that bandwidth pass visible light(400 to 740 nm), and multilayer dielectric coatings (22) that bandwidthpass infrared light (740 to 900 nm) are deposited on their respective P+tubs (14) and the N+ tubs (18) after deposition of the gold, chromium ortitanium adhesion and light block layer (14 a).

[0061] As shown in FIG. 10, the final three-inch wafer (30), withfabricated MMRI-4 square islands (8), is then removed from the four-inchsupport wafer (34). The three-inch wafer (30) is then rebonded to thefour-inch wafer (34) with an aqueous dissolvable adhesive. Using anexcimer laser, X and Y direction cuts are made to separate the MMIR-4islands (8) from each other. The MMRI-4 islands (8), however, stillremain bonded to the support wafer (34) by adhesive. The wafer assembly(30 and 34) is then placed in an aqueous solution solvent to dissolvethe adhesive. The MMRI-4 square islands (8) are recover from the aqueoussolution using standard filtering techniques, and are washed, and dried.The recovered MMRI-4 islands (8) are briefly tumbled in a glasscontainer using ultrasonic energy. This tumbling process will slightlyround off the sharp comers and edges of the MMRI-4s (8). The finaldevices, demonstrated by the MI-4s (8) of FIG. 7, are then washed again,recovered, sterilized, and then placed in a biologically compatiblesemisolid or liquid vehicle for implantation into the eye.

[0062]FIG. 11 shows MMRI-4s (8) implanted in their preferred monolayerposition in the subretinal space (82). The layers of the eye at theposterior pole from inside the eye to outside the eye are shown in theirrespective positions: internal limiting membrane (50); nerve fiber layer(52); ganglion and cell layer (54 ); inner plexiform layer (56); innernuclear layer (58); outer plexiform layer (60); outer nuclear cell layer(62); and photoreceptor layer (64), all of which constitute the innerretinal layer (66). The MMRI-4s (8) are disposed between the innerretinal layer (66), and the retinal pigment epithelium (68) and Bruch'smembrane (70), which together constitute the outer retinal layer (72).External to the outer retinal layer (72) are the choriocapillaris (74)and choroid (76) which comprise the choroidal vasculature (78), andsclera (80), which comprised the outer coat of the eye.

[0063]FIG. 12 shows MMRI-4s (8) in an alternate embodiment location,positioned on the internal limiting membrane surface (50) of the retinaand close to the nerve fiber layer (52). In this location, MMRI-4s (8)are embedded into a flexible, biologically compatible sheet (44), thatallows both of the flattened photoactive surfaces of each MMRI-4s (8) tobe exposed. Electrical stimulation of the retinal nerve fiber layer(52), through the internal limiting membrane surface (50) by the MMRI-4s(8) will also induce artificial vision, but the quality of imagesproduced will not be as well formed as from stimulation of the retinafrom the subretinal space (82) as shown in FIG. 11. The layers of theeye at the posterior pole from inside the eye to outside the eye, shownin their respective positions in FIG. 12, are: internal limitingmembrane (50); nerve fiber layer (52); ganglion cell layer (54 ); innerplexiform layer (56); inner nuclear layer (58); outer plexiform layer(60); outer nuclear layer (62); and photoreceptor layer (64), all ofwhich constitute the inner retinal layer (66). The retinal pigmentepithelium (68) and Bruch's membrane (70), together constitute the outerretinal layer (72). External to the outer retinal layer (72),choriocapillaris (74) and choroid (76) comprise the choroidalvasculature (78), and sclera (80), the outer coat of the eye.

[0064] As illustrated in FIGS. 13-16, in a further embodiment of theMMRI component of this invention, the two dielectric filter layersembedded in each MMRI will be both of the visible light transmittingtype (210, 222), or will be both of the IR light transmitting type (310,322). Instead of using polysilicon for their electrodes, the electrodesof these devices (202, 204, 302, 304) may be fabricated from gold,although aluminum or platinum may also be used, and will be depositedwith an industry standard “wafer bumping” process. This will form eachelectrode into a projecting-like structure bonded to an aluminum contactpad (214, 224, 314, 324). Each gold projecting electrode (202, 204, 302,304) will be then covered over its entire surface, with the exception ofthe tip, by an insulating layer of silicon dioxide (208, 226, 308, 326)or alternatively silicon nitrite. The height of the projecting electrodewill be higher on one side of the device than on the other side, and maybe 5 μm to 200 μm on the higher side (202, 302) and 1 μm to 195 ˜m onthe lower side (204, 304). When thus fabricated, these individualdevices are will form two populations: (1) a visible light responsivedevice (“MMRI-IPV”) designated at (200) with a higher projectingelectrode (HPE) (202) on the negative (N) side (205 b), and a lowerprojecting electrode (LPE) (204) on the positive (P) side (205 a), and(2) a IR light responsive device (“MMRI-IPIR”) designated at (300) witha HPE (302) on the P side (305 b) and a LPE (304) on the N side (305 a).

[0065] As illustrated in FIGS. 17-18, the two units, MMRI-IPV (200) andMMRI-IPIR (300), can also exist as a combination unit (MMRI-IPVIR-A)designated at (400), comprised of one MMRI-IPV (200) and one MMRI-IPIR(300). The HPE (202) of the MMRI-IPV (200) and the HPE (302) MMRI-IPIR(300) will be pointed in the same direction on the one side of theMMRI-IPVIR-A. The LPE (204) of the MMRI-IPV (200) and the LPE (304) ofthe MMRI-IPIR (300) will be also pointed together in the same direction,but on the opposite side of the MMRI-IPVIR-A (400) and in a directionopposite the direction of the HPEs (202, 302).

[0066] As illustrated in FIG. 21, the MMR-IPVIR-A (400) are disposed inthe subretinal space (82) of the eye, and are used to stimulate thoseretinas where the photoreceptor layer has completely degenerated leavingthe bipolar cell layer (58 a) or the inner plexiform layer (56) as thelayer adjacent to the subretinal space (82). Since the “light channel”inner plexiform layer known as sublamina “B” (56 b) is further away fromthe subretinal space (82) compared to the “dark channel” inner plexiformlayer known as sublamina “A” (56 a), the HPE electrodes (202, 302) willselectively contact the “light channel” synapses in the sublamina “B”(56 b) and the LPEs (204, 304) will selectively contact the “darkchannel” synapses in sublamina “A” (56A). This arrangement will allow avisible light stimulus to selectively depolarize and activate the lightchannels in sublamina “B” by causing a negative electric current to beproduced by the HPE (202), and an IR light stimulus to selectivelyhyperpolarize and inhibit the light channels in sublamina “B” by causinga positive electric current to be produced by the HPE (302). Thisarrangement will also allow an IR light stimulus to selectivelydepolarize and activate the dark channels in sublamina “A” by causing anegative electric current to be produced by the LPE (304), and a visiblelight stimulus to selectively hyperpolarize and inhibit the darkchannels in sublamina “A” by causing a positive electric current to beproduced by the LPE (204).

[0067] As illustrated in FIGS. 12 and 22, in another embodiment, MMRI-4(8), and reversed polarity MMRI-IPVIR-A implants called for convenience,MMRI-IPVIR-ARs (8 c), are embedded into a biologically compatible sheet(44) that allows the electrode surfaces of the devices to be exposed.

[0068] As shown in FIG. 12, the sheet (44), with the embedded MMRI-4 (8)is placed on the internal limiting membrane surface (50) of the retinafrom the vitreous body side. From this location, MMRI-4s (8) willstimulate the Nerve Fiber Layer (52) and/or Ganglion Cells (54) of theretina.

[0069] As shown in FIG. 22, in the case of the MMRI-IPVIR-ARs (8 c),their electrodes will penetrate the nerve fiber (52) and ganglion celllayer (54) into the sublamina “B” light channel layer (56 b), andsublamina “A” dark channel layer (56 a) regions of the inner plexiformlayer (56) to selectively stimulate those layers to induce visualsensations. The reverse polarity of the MMRI-IPVIR-ARs (8 c) compared tothe MMRI-IPVIR-As (400) of FIG. 21 is necessary to preserve the visiblelight stimulus's effect of depolarizing (activating) the light channelsof sublamina “B” (56 b) while hyperpolarizing (inhibiting) the darkchannels of sublamina “A” (56 a); and an IR light stimulus's effect ofdepolarizing (activating) the dark channels of sublamina “A” (56 a)while hyperpolarizing (inhibiting) the light channels of sublamina “B”(56 b). It should be noted that polarization changes, i.e.hyperpolarization and depolarization, do not have the same effect in thesubretinal space on remanent photoreceptor cells as they do in thesublamina B and A regions of the IPL. In the subretinal space, ahyperpolarizing stimulus produces a sensation of light in the remanentphotoreceptor cells while a depolarizing stimulus produces a sensationof darkness in remanent photoreceptor cells.

[0070] FIGS. 13-14 therefore illustrate a fifth embodiment of thisinvention referred to for convenience as a “MMRI-IPV”, and is sized inmicroscopic dimensions, and is designated at (200). MMRI-IPV (200) is aphysically independent unit with its layered microarchitecture shown inFIG. 14. In this embodiment, the MMRI-PV (200) forms the shape of aflattened cube with rounded corners and edges, with an electricallynegative high projecting electrode (“HPE”) (202), and an electricallypositive low projecting electrode (LPE”) (204). A MMRI-IPV (200) mayfunction as a PiN or NiP device when stimulating the inner retina,depending upon which of its two photosensitive sides, the P side (205 a)or the N side (205 b) is stimulated by visible light (206). From top tobottom, the layers of the MMRI-IPV (200) are as follows: A negative HPEelectrode (202) preferably made of gold, an insulating layer of SiO₂(208) which covers the N side (205 b) except for the tip of the HPEelectrode (202), a multilayer dielectric filter (210) to allow passageof only visible light (400 nm to 740 nm), a N+ layer (212), a contactpad (214) fabricated from any of the following, and/or any compounds ofthe following: gold, aluminum, titanium, and chromium, to establishelectrical contact between the negative HPE (202) and the N+ layer(212), a N-type silicon substrate layer (216), an intrinsic layer (218)which forms naturally between the N-type silicon substrate layer (216),and the next P+ layer (220), a multilayer dielectric filter (222) toallow passage of only visible light (400 nm to 740 nm), a contact pad(224) fabricated from any of the following, and/or any compounds of thefollowing: gold, aluminum, titanium, and chromium to establishelectrical contact between the P+ layer (220) and the electricallypositive low projecting electrode (LPE) (204). An insulating layer ofSiO₂ (226) covers the P side (205 a) except for the tip of the LPEelectrode (204).

[0071] FIGS. 15-16 illustrates a sixth embodiment of this inventionreferred to for convenience as a “MMRI-IPIR”, and is sized inmicroscopic dimensions, and is designated at (300). As illustrated, aMMRI-IPIR (300) is a physically independent unit with its layeredmicroarchitecture is shown in FIG. 16. In this embodiment, the MMRI-IPIR(300) forms the shape of a flattened cube with rounded corners andedges, with an electrically positive high projecting electrode (HPE)(302), and an electrically negative low projecting electrode (LPE)(304). The MMRI-IPIR (300) is sized in microscopic dimensions. AMMRI-IPIR (300) may function as a PiN or NiP device when stimulating theinner retina, depending upon which of its two photosensitive sides, theN-side (305 a) or the P-side (305 b) is stimulated by infrared light(306). From top to bottom, the layers of the MMRI-IPIR(300) are asfollows: A positive HPE electrode (302) preferably made of gold, aninsulating layer of SiO₂ (308) which covers the P side (305 b) exceptfor the tip of the positive HPE electrode (302), a multilayer dielectricfilter (310) to allow passage of only IR light (740 nm to 900 nm), a P+layer (312), a contact pad (314) fabricated from any of the followingand/or any compounds of the following: gold, aluminum, titanium, andchromium, to establish electrical contact between the positive HPE (302)and the P+ layer (312), an intrinsic layer (318) which forms naturallybetween the P+ layer (312) and the next N-type silicon substrate layer(316), a N+ layer (320), a multilayer dielectric filter (322) to allowpassage of only IR light (740 nm to 900 nm), a contact pad (324)fabricated from any of the following and/or any compounds of thefollowing: gold, aluminum, titanium, and chromium to establishelectrical contact between the N+ layer (320) and the electricallynegative low projecting electrode (LPE) (304). An insulating layer ofSiO2 (326) covers the N side (305 a) except for the tip of the LPEelectrode (304).

[0072] FIGS. 17-18 illustrate a seventh embodiment of this inventionreferred to for convenience as a “MMRI-IPVIR A”, and is sized inmicroscopic dimensions, and is designated at 400. It is composed of oneMMRI-IPV (200), and one MMRI-IPIR (300), separate by a layer of channelblock (350). The layered microarchitecture of the MMRI-IPV component(200) is shown on the left side and is described first. The MMRI-IPVcomponent (200) forms the shape of one-half of a flattened cube withrounded external comers and edges, with an electrically negative highprojecting electrode (HPE) (202), and an electrically positive lowprojecting electrode (LPE) (204). From top to bottom, the layers of theMMRI-IPV (200) are as follows: A negative HPE electrode (202) preferablymade of gold, an insulating layer of SiO2 (208) which covers the N side(205 b) except for the tip of the HPE electrode (202), a multilayerdielectric filter (210) to allow passage of only visible light (400 nmto 740 nm), a N+ layer (212), a contact pad (214) fabricated from any ofthe following and/or any compounds of the following: gold, aluminum,titanium, and chromium, to establish electrical contact between thenegative HPE (202) and the N+ layer (212), a N-type silicon substratelayer (216), an intrinsic layer (218) which forms naturally between theN-type silicon substrate layer (216), and the next P+ layer (220), amultilayer dielectric filter (222) to allow passage of only visiblelight (400 nm to 740 nm), a contact pad (224) fabricated from any of thefollowing and/or any compounds of the following: gold, aluminum,titanium, and chromium to establish electrical contact between the P+layer (220) and the electrically positive low projecting electrode (LPE)(204). An insulating layer of SiO2 (226) covers the P side (205 a)except for the tip of the LPE electrode (204). The layeredmicroarchitecture of the MMRI-IPIR component (300) of the MMRI-IPVIR-A(400) is shown on the right side and is now described. The MMRI-IPIRcomponent (300) forms the shape of one-half of a flattened cube withrounded external corners and edges, with an electrically positive highprojecting electrode (HPE) (302), and an electrically negative lowprojecting electrode (LPE) (304). From top to bottom, the layers of theMI-IPIR (300) are as follows: A positive HPE electrode (302) preferablymade of gold, an insulating layer of SiO2 (308) which covers the P side(305 b) except for the tip of the positive HPE electrode (302), amultilayer dielectric filter (310) to allow passage of only IR light(740 nm to 900 nm), a P+ layer (312), a contact pad (314) fabricatedfrom any of the following and/or any compounds of the following: gold,aluminum, titanium, and chromium, to establish electrical contactbetween the positive HPE (302) and the P+ layer (312), an intrinsiclayer (318) which forms naturally between the P+ layer (312) and thenext N-type silicon substrate layer (316), a N+ layer (320), amultilayer dielectric filter (322) to allow passage of only IR light(740 nm to 900 nm), a contact pad (324) fabricated from any of thefollowing and/or any compounds of the following: gold, aluminum,titanium, and chromium to establish electrical contact between the N+layer (320) and the electrically negative low projecting electrode (LPE)(304). An insulating layer of SiO2 (326) covers the N side (305 a)except for the tip of the LPE electrode (304).

[0073] FIGS. 19-20 illustrate an eighth embodiment of this inventionreferred to for convenience as a “MMRI-IPVIR-B”, and is sized inmicroscopic dimensions, and is designated at 500. It is composed of oneMMRI-IPV (200), and one MMRI-IPIR(300), separate by a layer of channelblock (350). The layered microarchitecture of the MMRI-IPV component(200) is shown on the left side and is described first. The MMRI-IPVcomponent (200) forms the shape of one-half of a flattened cube withrounded external corners and edges, with an electrically negative highprojecting electrode (HPE) (202), and an electrically positive lowprojecting electrode (LPE) (204). From top to bottom, the layers of theMMRI-IPV (200) are as follows: A negative HPE electrode (202) preferablymade of gold, an insulating layer of SiO₂ (208) which covers the N side(205 b) except for the tip of the negative UPE electrode (202), amultilayer dielectric filter (210) to allow passage of only visiblelight (400 nm to 740 nm), a N+ layer (212), a contact pad (214)fabricated from any of the following and/or any compounds of thefollowing: gold, aluminum, titanium, and chromium, to establishelectrical contact between the negative UPE (202) and the N+ layer(212), a N-type silicon substrate layer (216), an intrinsic layer (218)which forms naturally between the N-type silicon substrate layer (216),and the next P+ layer (220), a multilayer dielectric filter (222) toallow passage of only visible light (400 nm to 740 nm), a contact pad(224) fabricated from any of the following and/or any compounds of thefollowing: gold, aluminum, titanium, and chromium to establishelectrical contact between the P+ layer (220) and the electricallypositive low projecting electrode (LPE) (204). An insulating layer ofSiO₂ (226) covers the P side (205 a) except for the tip of the LPEelectrode (204). The layered microarchitecture of the MMRI-IPIRcomponent (300) of the MMRI-IPVIR-B (500) is shown on the right side andis now described. The MMRI-IPIR component (300) forms the shape ofone-half of a flattened cube with rounded external corners and edges,with an electrically positive high projecting electrode (HPE) (302), andan electrically negative low projecting electrode (LPE) (304). From topto bottom, the layers of the MMRI-IPIR (300) are as follows: A positiveHPE electrode (302) preferably made of gold, an insulating layer of SiO₂(308) which covers the P side (305 b) except for the tip of the positiveHPE electrode (302), a multilayer dielectric filter (310) to allowpassage of only IR light (740 nm to 900 nm), a P+ layer (312), a contactpad (314) fabricated from any of the following and/or any compounds ofthe following: gold, aluminum, titanium, and chromium, to establishelectrical contact between the positive HPE (302) and the P+ layer(312), an intrinsic layer (318) which forms naturally between the P+layer (312) and the next N-type silicon substrate layer (316), a N+layer (320), a multilayer dielectric filter (322) to allow passage ofonly IR light (740 nm to 900 nm), a contact pad (324) fabricated fromany of the following and/or any compounds of the following: gold,aluminum, titanium, and chromium to establish electrical contact betweenthe N+ layer (320) and the electrically negative low projectingelectrode (LPE) (304). An insulating layer of SiO₂ (326) covers the Nside (305 a) except for the tip of the LPE electrode (304).

[0074]FIG. 21 shows MMRI-IPVIR-As (400) implanted in their preferredmonolayer position in the subretinal space (82). The depolarizing highprojecting electrodes (HPEs) (202) from the visible light sensingportion of the microphotodiodes stimulate the light channels insublamina B (56 b) of the inner plexiform layer (IPL) (56). Thehyperpolarizing HPEs (302) from the IR light sensing portion of themicrophotodiodes (for darkness detection) inhibit the light channels insublamina B (56 b) of the IPL (56). The depolarizing low projectingelectrodes (LPEs) (304) from the IR light sensing portion of themicrophotodiodes (for darkness detection) stimulate the dark channels insublamina A (56 a) of the IPL (56). The hyperpolarizing LPEs (204) fromthe visible light sensing portion of the microphotodiode inhibit thedark channels in sublamina A (56 a) of the IPL (56). The layers of theeye, in this schematic of a partially degenerated retina, at theposterior pole from inside the eye to outside the eye are: internallimiting membrane (50); nerve fiber layer (52); ganglion cell layer(54); inner plexiform layer (56) consisting of sublamina b (56 b) andsublamina a (56 a); and the partially degenerated inner nuclear layer(58 a). The MMRI-IPVIR-A (400) are disposed between the partiallydegenerated inner retinal layer (66 a), and the retinal pigmentepithelium (68) and Bruch's membrane (70), which together constitute theouter retinal layer (72). External to the outer retinal layer (72) arethe choriocapillaris (74), choroid (76), and sclera (80). Alternatively,instead of MMRI-IPVIR-As (400), component MMRI-IPVs and MMRI-IPIRs ofFIGS. 13-16, or MMRI-IPVIR-Bs of FIGS. 19-20 can be implanted into thesubretinal space (82).

[0075]FIG. 22 shows MMRI-IPVIR-ARs (8 c) in a ninth embodiment of thisinvention, positioned on the internal limiting membrane surface (50) ofthe retina. In this embodiment, MMRI-IPVIR-ARs (8 c) are embedded into aflexible, biologically compatible sheet (44), which allows both of thephotoactive surfaces and their projecting electrodes of eachMMRI-IPVIR-ARs (8 c) to be exposed. The depolarizing high projectingelectrodes (HPEs) (302 a) on the opposite side of the IR sensingmicrophotodiodes (for darkness detection) penetrate into the darkchannels in sublamina A (56 a) of the inner plexiform layer (IPL) (56)to stimulate the sensation of darkness. The hyperpolarizing HPEs (202 a)on the opposite side of the visible light sensing portion of themicrophotodiodes penetrate into the sublamina A (56 a) of the IPL (56)to inhibit the dark channels. The depolarizing low projecting electrodes(LPEs) (204 a) on the opposite side of the visible light sensing portionof the microphotodiodes penetrate into sublamina B (56 b) of the IPL(56) to stimulate the light channels. The hyperpolarizing LPEs (304 a)on the opposite side of the IR light sensing portion of themicrophotodiode (for sensing darkness) penetrate into sublamina B (56 b)of the IPL (56) to inhibit the light channels. The layers of the eye atthe posterior pole from inside the eye to outside the eye in thisschematic of a partially degenerated retina are: internal limitingmembrane (50); nerve fiber layer (52); ganglion cell layer (54); innerplexiform layer (56) consisting of sublamina b (56 b) and sublamina a(56 a); the partially degenerated inner nuclear layer (58 a); all ofwhich constitute the partially degenerated inner retinal layer (66 a).The retinal pigment epithelium (68) and Bruch's membrane (70), togetherconstitute the outer retinal layer (72). External to the outer retinallayer (72) are the choriocapillaris (74), choroid (76), and sclera (80).In a subset embodiment, MMRI-IPVIR-ARs (8 c) may be fabricated ascomponent opposite polarity MMRI-IPVs and component opposite polarityMMRI-IPIRs, embedded into a flexible, biologically compatible sheet(44), which allows both of the photoactive surfaces and their projectingelectrodes of each opposite polarity MMRI-IPV and opposite polarityMMRI-IPIR to be exposed.

[0076]FIG. 23 is a schematic diagram of the Adaptive Imaging RetinalStimulation System (AIRES) showing its component sub-systems of: theProjection and Tracking Optical System (PTOS) headset (94), theNeuro-Net Computer (NNC) (96), the Imaging CCD Camera (IMCCD) (100) andthe Input Stylus Pad (ISP) (102). A Pupil Reflex Tracking CCD (PRTCCD)(98), and an IR/visible CRT display (IRVCRT) (92) is inside the PTOS(94). MMRI-4s (8) are shown in the subretinal space of the eye (90).During function, IR and visible light images from the IRVCRT (92) withinthe PTOS (94) are optically projected onto the eye (90). Intensity,wavelength duration, and pulsing of the images is controlled by the NNC(96) and modulated by patient inputs via the interfaced ISP (102). TheIMCCD (100), which is mounted on or in the PTOS headset (94), providesthe image inputs to the NNC (96) which in turn programs the visible andIR image outputs of the IRVCRT (92). A PRTCCD (98) is integrated intothe PTOS headset (94) to track eye movements via changes in the positionof the pupillary Purkinje reflexes. The PRTCCD (98) will output to theNNC (96) which in turn will direct the aim of the IMCCD (100) via servomotor control to follow the eye movements. The PTOS (94) also may beprogrammed to provide just a diffuse IR illumination to interact withambient visible light images (104) on the MMRI-4s (8).

[0077] The detailed operation of the AIRES system is as follows. Apatient with a large plurality of implanted MMRI-4s (8) will seepixelated images, cause by localized subretinal hyperpolarization,produced by the PiN configuration of the MMRI-4 subunits (10 a). Theseelectrically induced images are caused by the light from incomingambient images (104) which pass through an external partially reflectiveand transmissive mirror (106) of the PTOS (94). Images of dark detailsare induced by depolarizing currents produced by the NiP configurationof MMRI-4 subunits (10 b), which are stimulated by IR illuminationand/or images provided by the IRVCRT (92). The IRVCRT (92) is programmedby the NNC (96) to provide diffuse IR illumination and/or IR images tosuperimpose upon the visible light images (104) from incoming light.Image information for the NNC (96) is obtained from the interfaced IMCCD(100). Diffuse IR illumination from the IRVCRT (92) will induce aconstant depolarizing “bias current” from the MMRI-4 NiP subunits (10b). This “bias current” will produce the sensation of darkness in theabsence of light stimulation to the PiN subunits (10 a). However, whenlight is present to stimulate the PiN subunits (1 a), the resultanthyperpolarizing current will offset the IR induced NiP depolarizing biascurrent. The result is the perception by the patient of a sensation oflight. Because of the limited bandwidth sensitivity of the IR NiPconfiguration (10 b) (740 nm-900 nm), environmental IR “noise” isminimal. The amount of NiP depolarizing bias current will be initiallyadjusted by the patient via the ISP (102) and this information will beinput into the NNC (96). It is then correlated with image processedinformation coming from the interfaced IMCCD (100). The appropriateamount of NiP “bias current”, base upon environmental lightingconditions and images, will then be “learned” by the NNC (96). Withadditional learning, the NNC (96) will be able to anticipate the amountof NiP “bias current” needed to produce more accurate patient perceivedimages, without the need for patient input.

[0078] The entire visible light image may also be projected by theIRVCRT (92) simultaneously, or in rapid alternation with IR image pulsesto entirely control MMRI-4(B) function. In this situation, the partiallyreflective/transmissive mirror (106) of the PTOS (94), is replaced witha completely reflective mirror, to prevent ambient light images (104)from stimulating the MMRI-4s (8). By programming the pulse duration andfrequency of IR and visible-light images, color vision may possibly beinduced, similar to the effect of the Benham top. This phenomenon hasalso been used in black and white television displays to create theperception of color images in normal sighted persons.

[0079]FIG. 24, A through D shows a glasses-like configuration (94) ofthe PTOS component of the AIRES system. As seen in FIG. 24D, althoughthe schematic of the optical system differs somewhat from the generalizeschematic of the PTOS component (94) demonstrated in FIG. 23, the spiritand function of both versions of the devices are the same. FIG. 24A is atop view of the PTOS (94). It shows the head-pad (108), the templepieces (110), and the ambient light intensity sensors (112). FIG. 24B isa front view of the PTOS (94). It shows the external partiallyreflective/transmissive mirror (106), a supporting nose piece (114),ambient light intensity sensors (112), and the window for the IMCCD(100) shown in the FIG. 23 schematic. FIG. 24C is a phantom side view ofthe PTOS (94). It shows an internal infrared and visible light capableLED light source (92), which has been substituted for the IRVCRT (92) ofFIG. 23. Also shown is the partially reflective/transmissive mirror(106), the supporting nose piece (114), the head-pad (108), one of thetemple pieces (110), and the power supply and signal wire cable (116) tothe NNC (96) of FIG. 23. FIG. 24D is a schematic of the PTOS (94). Itshows the MMRI-4s (8) disposed in the subretinal space of the eye (90)with an ambient focused image (104). It also shows the internal infraredand visible light capable LED light source (92), the PRTCCD (98), andthe external partially reflective/transmissive mirror (106).

[0080]FIG. 25 is diagram showing the components of the AIRES system,consisting of the PTOS (94), the portable NNC (96) which may be securedto the patient's body, and the ISP (102) input device.

[0081]FIG. 26 is a plan view (containing a detail exploded inset view)of a large wafer containing a ninth embodiment of an implant of thisinvention. This ninth embodiment is based on a microphotodiode (401 a)(referred to hereinafter as an “MMRI-OPSISTER-D”). Each MMRI-OPSISTER-Dmicrophotodiode (401 a) has two microphotodiode subunits (402) and(404), as shown in the exploded inset view in FIG. 26.

[0082] As will be discussed below, the large wafter (405) can be cutinto smaller wafer-type implants (e.g. wafers of about 0.25 to 15 mn(e.g. thousands to tens of thousands) of MMRI OPSISTER-D microphodiodeunits (401 a). Alternately, large wafer (405) can be diced into evensmaller discrete-type implants (e.g. implants of between 1 micron and0.25 mm containing one to 10,000 MMRI OPSISTER-D micropholodiode units(401 a). Whether a wafer-type implant or discrete implants are made,many of the fabrication steps and the basic structure of the MMRIOPSISTER-D micropholodiode (401 a) is the same.

[0083] FIGS. 27 A-E illustrate, in perspective cross-sectional viewstaken at section XXVII-XXVII of the MMRI-OPSISTER-D (401 a) of FIG. 26,the fabrication steps and structure of the MMRI-OPSISTER-D (401 a). Inthe initial fabrication step (FIG. 27A) microphotodiode subunits (402)and (404) of the MMRI-OPSISTER (401) are formed using photomask, ionimplantation and heat drive-in techniques applied to both sides of astarting N bulk thinned wafer (405 of FIG. 26). From top to bottom inFIG. 27A, the microphotodiode subunit (402) has a P+ layer (406), anintrinsic layer (408), an N bulk layer (409) and a N+ layer 410. Themicrophotodiode subunit (404) has a N+ layer (410 a), an N bulk layer(409 a), an intrinsic layer (408 a) and a P+ layer (406 a). Separatingelectrically the two microphotodiode subunits (402 and 404) from oneanother and from other MMRI-OPSISTERs on the same substrate is P+channel block (412) surrounding the subunits (402 and 404).

[0084]FIG. 27B shows aluminum contact pads (418 a-d) that are depositedand heat driven-in into the P+ and N+ surfaces (406, 406 a, 410, and 410a). Bridging the contact pads (418 a-d) between the P+ and N+ surfaces(406, 406 a, 410, and 410 a) of each side of the MMRI-OPSISTER (401) isa silicon dioxide insulator strip (414 a and 414 b).

[0085]FIG. 27C shows the deposition of aluminum conductors (415 and 415a) over the silicon dioxide insulator strips (414 a and 414 b) so thatthe conductor (415) contact the aluminum contact pads (418 a and 418 b),and conductor (415 a) contact the aluminum contact pads (418 c and 418d).

[0086]FIG. 27D shows the deposition of infrared-pass dielectric filters(422 and 422 a) on the P+ surfaces (406 and 406 a), andvisible-light-pass dielectric filters (424 and 424 a) on the N+ surfaces(410 and 410 a). A layer of barrier aluminum (417) needed during thefabrication of dielectric filters (422 and 424) is also deposited on theconductor (415). Similarly another layer of barrier aluminum (417 a)needed during the fabrication of dielectric filters (424 a and 422 a) isdeposited on the conductor (415 a).

[0087]FIG. 27E shows the deposition of the final bridging electrode(420) on the barrier aluminum (417), and the deposition of the finalbridging electrode (420 a) on the barrier aluminum (417 a). The finalbridging electrodes (420 and 420 a) are fabricated from anybiocompatible electrode material or combinations of biocompatibleelectrode materials such as iridium, platinum, gold, aluminum,ruthenium, rhodium, palladium, tantalum, titanium, chromium, molybdenum,cobalt, nickel, iron, copper, silver, zirconium, tungsten, polysilicon,or compounds, such as oxides, composed of the same. Iridium oxide is thepreferred material for the electrodes (420 and 420 a). The MMRI-OPSISTERdevice (401) of FIGS. 27A-C with dielectric light filters is called anMMRI-OPSISTER-D device (401 a) in FIGS. 27D, E.

[0088] As shown in FIG. 27E, the dielectric light filter layers (422,422 a, and 424, 424 a) allow only specific, but different, lightbandwidths to pass. In the embodiment illustrated in FIG. 27E, thedielectric filter layers (422 and 422 a) that overlay the P+ layers (406and 406 a) allow only IR light to pass, whereas the dielectric layers(424 and 424 a) that overlay the N+ layers (410 and 410 a) allow onlyvisible light to pass. In other embodiments, the two types of layers canbe reversed where the visible light filters are deposited on the P+layers, and the IR light filters are deposited on the N+ layers. Instill other embodiments, filters (422, 422 a), and filters (424, and 424a) can allow different portions of visible or- infrared light to pass (e.g. filters 422 and 422 a allow only green light to pass and filters424, 424 a allow only red light to pass).

[0089] The MMRI-OPSISTER-D device (401 a) functions to stimulate visionfrom the subretinal space (82) (see FIG. 11). As discussed above,implants (401 a) may be diced into discrete physically separate devicesas shown in FIG. 27E. In this circumstance, MMRI-OPSISTER-D devices (401a) are placed into the subretinal space (designated as 82 in FIG. 11) byinjection using a liquid vehicle or embedded in a dissolvable sheet(both previously described).

[0090] As discussed above, large wafer (405) of FIG. 26 can be cut intosmaller wafer-type implants (405 a) (see FIG. 28) of a width (ordiameter) ranging from 0.25 mm to 15 mm, preferably from 0.25 mm to 2mm. Preferably, the edges of implant (405 a) are rounded or beveled asshown in FIG. 28 to reduce the possibility of the overlaying nerve fiberlayer nerve transmission being reduced by a sharp bend in that layernear the edge of the implant.

[0091] One or more of the wafer-type implants (405 a) can then beimplanted into the subretinal space (82) between the inner retina (66)and the outer retina (78).

[0092] To understand the operation of each MMRI-OPSISTER-D unit (401 a)(e.g. the one shown in FIG. 27), one should consider the function of anormal, undamaged photoreceptor cell in an eye, and how light and darkimages are sensed. In the normal retina, light causes the photoreceptorcell to become more negatively charged internally, whereas the lack oflight or a dark image will cause the photoreceptor cell to become lessnegatively charged internally. The greater internal negativity willcause a signal to be transmitted by the photoreceptor cell to one typeof associated bipolar cell which signals that light is sensed. Thelesser internal negativity will cause a signal to be transmitted by thephotoreceptor cell to another type of associated bipolar cell thatsignals that darkness (or a dark image) is sensed. These different typesof bipolar cells are associated with their respective amacrine andganglion cells that convert the analog signals of light and darknessproduced by the bipolar cells into digital signals that are then sent tothe brain and processed as visual information.

[0093] As discussed above, therefore, functionally one predominantbandwidth of light shining on the MMRI-OPSISTER-D (401 a) (e.g. visiblelight or a portion thereof, say green light) will cause current of onepolarity to be generated from one electrode (420) and the oppositepolarity from the other electrode (420 a), while a different predominantbandwidth of light (e.g. IR, or a different portion of visible light,say red light) shining on the MMRI-OPSISTER-D (401 a) will cause currentof reversed polarity to be generated from the electrodes (420 and 420 a)(as compared to the electrodes 420 and 420 a polarity from visible lightstimulation in the first situation). Specifically, in typicalillumination conditions, light composed of mixtures of differentbandwidths will be found. Depending on the predominant bandwidthencountered, either the P+ or the N+ layer will receive greater lightintensity, and be stimulated more intensely than the other, as a result.Therefore, one polarity of current will be generated from e.g. electrode(420) in one lighting condition predominant in one bandwidth, whereas adifferent polarity of current will be generated from electrode (420) inlighting conditions predominant in another bandwidth. In the orientationof the MMRI-OPSISTER-D (401 a) of FIG. 27E within the subretinal space,light (430) is coming from the top. Electrode (420) is the stimulatingelectrode of the inner retina (66) as shown in FIG. 11 because it is indirect contact with that portion of the retina. The electrode (420 a)which develops a opposite-polarity current to electrode (420) is facingaway from the inner retina and serves as the electrical return ofcurrent from electrode (420). Because the MMRI-OPSISTER-D (401 a) is asymmetric device, orientation of the MMRI-OPSISTER-D (401 a) with eitherelectrode (420) or electrode (420 a) facing the inner retina andincoming light (430), produces the same stimulation polarity of theinner retina.

[0094] In typical patients with macular degeneration, for example, thelight-sensing portion of the photoreceptor cell(s) is damaged or lost,leaving the remaining photoreceptor. When a device such as theMMRI-OPSISTER-D (401 a) shown in FIG. 27E is placed into the subretinalspace (82) of FIG. 11 in the same location as, but instead of theMMRI-4's (8), in contact with the remnant photoreceptor cells (64), andthe appropriate bandwidth of light (e.g. visible light or a portion ofthat spectrum, say green light as discussed above) stimulates the N+surface of the device facing incident light, the negative chargesproduced by the N+ surface of the device will induce a greaternegativity in the internal portion of the remnant photoreceptor cellsand create the sensation of light. In this example, the greater internalnegativity in this location causes a signal representing light sensationto be transmitted to the bipolar cell responsible for transmitting thesensation of light.

[0095] Likewise, when a device such as the MMRI-OPSISTER-D (401 a) shownin FIG. 27E is placed in the subretinal space (82) of FIG. 11 in thesame location as, but instead of the MMRI-4's (8), in contact with theremnant photoreceptor cells (64), and the appropriate bandwidth of light(e.g. IR light or a different portion of the spectrum, say red light asdiscussed above) stimulates the P+ surface of the device facing incidentlight, the positive charges produced by the P+ surface of the devicewill induce a lesser negativity in the internal portion of the remnantphotoreceptor cell and create the sensation of darkness or dark hues. Inthis example, the lesser internal negativity in this location will causea signal representing a sensation of darkness or dark hues to betransmitted to the appropriate bipolar cell responsible for transmittingthe sensation of darkness or dark hues.

[0096] The bridging electrodes (420, 420 a) allows the P+ and N+surfaces to electrically stimulate the retina through the sameelectrode. This is important to reduce the possibility of tissue injurydue to prolonged exposure to currents that may flow in only onedirection. However, it is believed that very little current is neededand will be induced to flow in the subretinal space by any of thedevices disclosed herein. The provision of bridging electrodes (420, 420a) is done simply as a precaution. However, bridging electrodes alsoallow the MMRI-OPSISTER-D device to stimulate smaller areas of theretina, and therefore produce higher resolution, than other embodimentsof this invention.

[0097] As shown in FIG. 27E, the MMR-OPSISTER-D devices (401 a) aretypically on the order of 10 microns thick but may vary from 3 micronsto 1000 microns in thickness.

[0098] As shown in FIG. 28, the small silicon disc (405 a) with itsMMRI-OPSISTER-D devices (401 a), shown implanted in the subretinal space(82), is typically on the order of 40 microns thick but may vary from 3microns to 1000 microns in thickness.

We claim:
 1. A retinal implant for electrically inducing formed visionin the eye, comprising a PiN microphotodiode where the P side of theimplant has a light filter layer that selectively permits a selectedbandwidth of the ultraviolet, visible, and infrared spectrum to pass,and where the N-side of the implant has a light filter layer thatselectively permits the a selected bandwidth of the ultraviolet,visible, and infrared spectrum to pass, whereby the retinal implant canstimulate the retina regardless of whether the P-side or the N-side isoriented toward light incident to the eye.
 2. The retinal implant ofclaim 1 wherein the N-side and the P-side filter layers selectivelypermit substantially the same bandwidth to pass.
 3. The implant of claim2 wherein the N-side light filter layer is a dielectric filter thatallows 740 nm to 900 nm to pass
 4. The implant of claim 3 wherein theP-side light filter layer is a dielectric filter that allows 740 nm to900 nm to pass 5 The implant of claim 2 wherein the N-side light filterlayer is a dielectric filter that allows 400 nm to 740 nm to pass. 6.The implant of claim 5 wherein the P-side light filter layer is adielectric filter that allows 400 nm to 740 nm to pass.
 7. The retinalimplant of claim 1 wherein the N-side and the P-side filter layersselectively permit substantially different bandwidth to pass.
 8. Theimplant of claim 7 wherein the N-side light filter layer is a dielectricfilter that allows 740 nm to 900 nm to pass.
 9. The implant of claim 8wherein the P-side light filter layer is a dielectric filter that allows400 nm to 740 nm to pass.
 10. The implant of claim 7 wherein the N-sidelight filter layer is a dielectric filter that allows 400 nm to 740 nmto pass.
 11. The implant of claim 10 wherein the P-side light filterlayer is a dielectric filter that allows 740 nm to 900 nm to pass. 12.The retinal implant of claim 1 wherein the PiN microphotodiode contains(1) a P-electrode made of P-doped polysilicon, (2) a P-side light filterdielectric layer, (3) a P+ layer, (4) an intrinsic layer, (5) a N-typesilicon substrate, (6) a N+ layer, (7) a N-side light filter dielectriclayer, and (8) a N electrode made of a N-doped polysilicon.
 13. Theretina implant of claim 12 wherein the implant further includes a firstelectrical contact pad that establishes electrical contact between theP-electrode and the P+ layer, and a second electrical contact pad thatestablishes electrical contact between the N-electrode and the N+ layer.14. The implant of claim 1 wherein the implant includes two of said PiNmicrophotodiodes, each of the microphotodiodes having an oppositeorientation from the other such that when implanted in the eye, theP-side of one microphotodiode will face incident light, and the N-sideof the other microphotodiode will face incident light.
 15. The retinalimplant of claim 12 wherein, the P-electrode projects outwardly from thesurface of the implant.
 16. The retinal implant of claim 12 wherein, theN-electrode projects outwardly from the surface of the implant.
 17. Theretinal implant of claim 15 wherein, the N-electrode projects outwardlyfrom the surface of the implant.
 18. The retinal implant of claim 17wherein, each of the P-electrode and N-electrode projects from about 1micron to about 200 microns.
 19. The retinal implant of claim 18wherein, each of the P-electrode and N-electrode projects from about 2micron to about 100 microns.
 20. The retinal implant of claim 14 whereina common electrode is in electrical contact with both the P-surface andthe N-surface on one side of the implant and another common electrode isin electrical contact with both the P-surface and the N-surface on theother side of the implant.
 21. The retinal implant of claim 20 wherein aplurality of the said implants are fabricated upon a common siliconsubstrate wafer.
 22. The retinal implant of claim 21 wherein the commonsilicon substrate wafer has a beveled edge.
 23. A method of restoringformed vision to a patient having retinal damage, comprising implantingplural implants into the patient's eye adjacent the retina, each implantcomprising a PiN microphotodiode where the P side of the implant has alight filter layer that selectively permits a selected bandwidth of theultraviolet, visible, and infrared spectrum to pass, and where theN-side of the implant has a light filter layer that selectively permitsthe a selected bandwidth of the ultraviolet, visible, and infraredspectrum to pass, whereby the retinal implant can stimulate the retinaregardless of whether the P-side or the N-side is oriented toward lightincident to the eye.
 24. The method of claim 23 where the P side of eachimplant has a light filter layer that selectively permits only visiblelight to pass, and where the N-side of each implant has a light filterlayer that selectively permits only infrared light to pass.
 25. Themethod of claim 23 wherein a population of such implants are implantedin the “subretinal space” between the outer and inner retina in the eyesuch that, randomly, about half of them (i.e. the first subpopulation)will be oriented so that the P sides face light incident to the eye, andabout half (i.e. the second subpopulation) will be oriented so thattheir N sides face incident light to the eye.
 26. The method of claim 24wherein a population of such implants are implanted in the “subretinalspace” between the outer and inner retina in the eye such that,randomly, about half of them (i.e. the first subpopulation) will beoriented so that the P sides face light incident to the eye, and abouthalf (i.e. the second subpopulation) will be oriented so that their Nsides face incident light to the eye.
 27. The method of claim 26 whereinthe first subpopulation of microscopic implants-convert energy fromincoming visible light into small electrical currents to stimulate thesensation of light detail in the eye to produce formed vision, and thesecond subpopulation converts infrared light induced electrical currentto stimulate the retina with dark current to produce dark details. 28.The method of claim 27 wherein infrared light is introduced into the eyeby an externally-worn unit containing an IR-capable image-producingdevice, whereby in darkness IR illumination is the predominate powersource and powers the second subpopulation, stimulating the visualsensation of dark details.
 29. The method of claim 28 wherein saidIR-capable image producing device is also visible-light capable whereinunder conditions displaying light and dark details, a current will beinduced in the first subpopulation by ambient visible light, and acurrent is induced in the second subpopulation by IR light, producing acombined perception of light and dark details.
 30. The method of claim29 wherein said externally-worn unit farther includes an imaging CCDcamera to capture real-time images, and further includes computer meansto digitize those images and transmit those images to saidimage-producing device.
 31. The method of claim 30 wherein saidreal-time images produced by the image-producing device are presented tothe retina superimposed on the visible and infrared real, ambientimages.
 32. The method of claim 31 wherein the images produced by imageproducing device are presented either simultaneously or in rapidsuccession with real, ambient images.
 33. The method of claim 32 whereinthe patient is provided with a patient input device interfaced with thecomputer means to allow the patient to modify the IR and visible-lightimages produced by said externally-worn unit.
 34. An implant forcreating formed vision in the eye, comprising at least twomicrophotodiode subunits, each of the two subunits having opposite PiNand NiP orientations whereby when the implant is placed in the eye so asto receive incident light, one of the subunits has a PiN configurationrelative to incident light and the other subunit has a NiP configurationrelative to incident light.
 35. The implant as recited in claim 34wherein the two subunits are symmetrical and have positive poleelectrodes on opposite surfaces of the implant and negative poleelectrodes on opposite surfaces of the implant, whereby the implant canfunction in the same manner regardless of which of the two surfacesfaces light incident to the eye.
 36. The implant as recited in claim 35comprising plural pairs of said two subunits.
 37. The implant as recitedin claim 36 wherein the implant comprises two pairs of said twosubunits.
 38. The implant as recited in claim 34 wherein the implant isbetween 1 micron and 1000 microns wide and long, and wherein thethickness of the implant is between about 1 to 500 percent of its width.39. The implant as recited in claim 34 wherein the implant is betweenabout 10 microns and about 50 microns wide and long, and wherein thethickness of the implant is between about 25 to 50 percent of its width.40. A method of restoring formed vision to a patient having retinaldamage, comprising implanting plural implants into the patient's eyeadjacent the retina, each implant comprising at least twomicrophotodiode subunits, each of the two subunits having opposite PiNand NiP orientations whereby when the implant is placed in the eye so asto receive incident light, one of the subunits has a PiN configurationrelative to incident light and the other subunit has a NiP configurationrelative to incident light.
 41. The method of claim 40 wherein the twosubunits of each implant are symmetrical and have positive poleelectrodes on opposite surfaces of the implant and negative poleelectrodes on opposite surfaces of the implant, whereby the implant canfunction in the same manner regardless of which of the two surfacesfaces light incident to the eye.
 42. The method of claim 41 wherein eachimplant comprises plural pairs of said two subunits.
 43. The method ofclaim 42 wherein each implant comprises two pairs of said two subunits.44. The method of claim 40 wherein each implant is between 1⁻ micron and1000 microns wide and long, and wherein the thickness of the implant isbetween about 1 to 500 percent of its width.
 45. The method of claim 44wherein the implant is between 10 and 50 microns wide and long, andwherein the thickness of the implant is between about 25 and 50 percentof its width.
 46. The method of claim 44, wherein a plurality of saidimplants are embedded into a biologically compatible sheet, and whereinthe sheet with the embedded devices is placed in the subretinal space.47. The method of claim 46 wherein the sheet with the embedded devicesis placed on the nerve fiber layer surface from the vitreous side. 48.The method of claim 47 wherein the sheet may be fabricated from abiologically degradable material.
 49. The method of claim 40 whereinsaid implants are implanted on the nerve fiber layer surface.
 50. Amethod of restoring formed vision to a patient having retinal damage,comprising implanting plural implants into the patient's eye on thenerve fiber layer, each implant comprising a PiN microphotodiode wherethe P and the N electrodes each contain a projection such that the atleast some of the P and the N electrodes of the plural implantspenetrate into each of the sublamina “A” and “B” layers of the innerplexiform layer.
 51. A retinal implant comprising two groups ofmicrophotoelectric subunits formed on a substrate, the two groups beingof opposite orientation: a first group of at least one PiN subunits, anda second group of at least one NiP subunits, such that the P+ layer ofthe first group is adjacent the N+ layer of the second group.
 52. Theretinal implant of claim 51 further comprising a first common electrodecontacting the P-surface of at least one of the subunits of the firstgroup to the N-surface of a second group subunit, and a second commonelectrode contacting the N-surface of at least one of subunits in thefirst group to the P-surface of a second group subunit.
 53. The retinalimplant of claim 52 wherein each PiN subunit is paired with an NiPsubunit, and each paired PiN/NiP subunit combination has a first andsecond common electrode.
 54. The retinal implant of claim 53 comprisingplural paired PiN/NiP subunit combinations.
 55. The retinal implant ofclaim 54 wherein the plural paired PiN/NiP subunit combinations are on asubstrate from 1 micron to 0.25 mm in width.
 56. The retinal implant ofclaim 54 wherein the plural paired PiN/NiP subunit combinations are on asubstrate from 0.25 mm to 15 mm in width.